I found myself pondering this very question while exploring the bottom of the Grand Canyon. Sure, help comes, but how? Who tells them where I am? Will someone call my emergency contact? How do my emergency contacts factor into my rescue?
Trying to find an answer I stumbled upon an article that pretty much sums everything up and even provides some tips for your best chance of survival!
You can find it here. Be ready for a rescue....hopefully it is never needed!